The present invention relates to laser/detector hybrids for use in optical heads.
This inventor disclosed in U.S. Pat. No. 4,731,772 an optical head consisting of a laser/detector hybrid device and holographic optical elements forming an optical head for reading signals from an optical disc. FIG. 1 shows the hybrid device 68 of that invention. The laser diode is of the type that emits light from the edge of the laser chip. Laser chip 86 is mounted on one surface of a heatsink 88 parallel to the direction of propagation of the light beam (out of the page). A photodetector 90 is mounted on a second surface of the heatsink which is normal to the direction of propagation of the light beam. A power monitor 92 is located behind the laser chip 86.
This inventor also disclosed in U.S. Pat. No. 4,906,839 an improvement of the hybrid device in U.S. Pat. No. 4,731,772 by mounting a surface emitting laser chip 18 directly on the surface of a photodetector chip 22 to form a hybrid device 200 as shown in FIG. 2. The light beam emitted by a surface laser is by its nature normal to the surface of the laser chip. In FIG. 2 the surface emitting laser is shown to be an edge emitting laser with a micro mirror edge cut into the laser chip substrate. Other types of surface emitting lasers are possible without the use of a micro mirror. With the surface emitting laser diode the manufacturing process of the hybrid device requires only die bonding the laser chip on a photodetector and then bonding the photodetector to a supporting substrate. Wire connections to all the components can be performed at the same time on the same plane. As a result, the manufacturing process for a hybrid device using surface emitting lasers is considerably simpler than those using edge emitting lasers as described in U.S. Pat. No. 4,731,772. For the edge emitting laser, the device must be wire bonded in one plane, and then rotated for the remaining wire bonds. FIG. 3 shows the optical head from U.S. Pat. No. 4,731,772 which uses a hybrid device 68 and holographic lens 74 for the reading of information from an optical disc. It is the objective of this invention to disclose a method whereby the same ease of manufacturing can be applied to the edge emitting laser diode.